A New Homogeneous Non-Equilibrium Model to Compute Vapor-Liquid Two-Phase Critical Pressure Ratios of Multicomponent Hydrocarbon Mixtures

• Published in: Journal of loss prevention in the process industries 2020-11, Vol.68, p.104338, Article 104338
• Main Authors: Jia, Wenlong, Ban, Jiuqing, Liang, Fangjian, Cheng, Tingting, He, Yufa, Li, Changjun
• Format: Article
• Language: English
• Subjects: Critical pressure ratio; Mathematical model; Multi-component gas mixture; Vapor-liquid two-phase flow
• ISSN: 0950-4230
• DOI: 10.1016/j.jlp.2020.104338

The critical pressure ratio (ηc) is an essential parameter for computing the vapor-liquid two-phase critical pressure and mass flow rate of multicomponent hydrocarbon mixtures flowing through valves and leakage orifices. The Homogeneous Non-Equilibrium Diener-Schmidt (HNE-DS) model widely used to calculate ηc assumes that the fluid's volume linearly changes with the pressure (using the Clausius-Clapeyron equation), which is not suitable for multicomponent gas mixtures. In this paper, a new Homogeneous Non-Equilibrium (new-HNE) model is proposed to calculate ηc of gas mixtures. Firstly, a new critical flow compressibility factor (ωc) is developed from its thermodynamic definition and the Peng-Robinson equation of state (EOS), overcoming the inherent limitations of the Clausius-Clapeyron equation. Then, ηc is correlated to the newly derived ωc by fitting experimental data at various pressures and gas mass fractions of both single-component and multicomponent gas mixtures, yielding the new HNE-DS model. Results show that, for the water-steam and air-water two-phase flow, the average relative deviations (ARD) between the calculated critical pressure ratios and experimental values are equal to 2.8% and 4.93%, respectively, which represents a significant improvement in comparison with the original HNE-DS model. Moreover, this new model is extended to the applications of Liquefied natural gas (LNG)/liquefied petroleum gas (LPG) fluids, and will further contribute to the calculation of the leakage mass flow rate of fluid flowing through the orifices/valves. •A new model is built to calculate the two-phase critical pressure of mixtures.•A new critical compressibility factor correlation is proposed.•The new model is validated by experimental data at various conditions.•The new model has high accuracy for multicomponent gas mixtures.